Checking irrigation design PSI from above ground storage tank

[James Andrew]

I am actually working out a design for irrigation using above ground storage tanks , and I want to check two things: 1) HP Size of the sprinkler pump 2) Cycle Stop Valve PSI

Current Plan:
Setting up sprinkler zone with 1 1/4 (poly) main line to feed 3 different control boxes.

--The main line is a direct line extending 320 feet. 1st Control box- 70 feet from pump, 2nd -150ft, 3rd- 320 ft (Friction Loss in 300' 1 1/4 poly pipe= 3psi)

-- Each zone will be configured up to 10-12 gpm in sprinkler head output, extending laterally no than 100ft of 1 inch poly pipe. (Friction Loss in 1 =3.82) Mostly rainbird rotary sprinklers, some smaller emitting heads too for flower beds.

Therefore Total Friction Loss in Piping= -6.83 psi at furthest zone, -4.5 psi at closest zones
-NO ELEVATION issues

-I am not sure what if any friction loss will be caused by the irrigation control valve itself. I cannot see to find any stats on that at all.

Conclusion-Question:
So I am thinking a 60 psi Cycle Stop Valve with 2 hp pump, 50-70 pressure switch, 4 gallon pressure tank. Does this sound right?

 

[Reach4]

A submersible pump in a flow inducer sleeve inside of the tank would need about 1/2 the HP you would need with a jet pump. The pump can be horizontal.

 

[Sponsor]

 

[James Andrew]

A submersible pump in a flow inducer sleeve inside of the tank would need about 1/2 the HP you would need with a jet pump. The pump can be horizontal.

Interesting possibility- but I do not relish trying to fit one through the 6 inch opening at top of tank (I am using IBC Totes) . Doable but not as neat an install as piping from the bottom to an external pump.

If I use the formula for feet to determine pump size I come up with 127 feet, at 12gpm, so this model of cistern pump looks more enticing because of its bottom feed upright mount: https://www.wholesalesepticsupply.c...ic-c1-20xc1-05p4-2w115-septic-pump-with-float Pump graph on the 20x version looks good. A bit pricey though.

 

[James Andrew]

What sayeth valveman ?

 

[Drick]

I have the 20XC1-05P4-2W230 installed in a 3000 Gallon cistern connected to a 14 zone Rainbird irrigation system. I have 400 feet of mainline with approximately 10 feet of uphill grade on it. My mainline is 1.25 inch 160PSI poly. My largest zone is 18 GPM and it comes in right on the pump curve at approx 45 PSI. I've had the pump for 5 years with no problems. I would say definitely get it except for the fact your totes are literally set up to work with a jet pump. Hmm tough choice... Either way you will need a low water float switch in the tank somehow.

As for the CSV I don't have one, but I think its a good idea. Although you can control the pump with a start relay you need to consider the possibility that some day a zone valve will fail to open. If it fails to open and the pump is running dead headed you will probably burn up the pump before you realize you have a problem. Don't count on a pressure relief valve to work if you want 60 PSI operating pressure for your sprinklers and want the relief valve to open at 80 psi. My personal experience is the differential between the two doesn't seem to be enough to get the valve to open reliably. Another advantage of the CSV is you could install faucets off your main line if you wanted to use a garden hose.

 

[Valveman]

For that much flow and using a 50/70 pressure switch you will need something like a J15S jet pump. Those bottom feeding "cistern" submersible pumps don't have the bearing structure and meat in them of a regular well pump submersible, and I haven't seen one last very long. With the J15S pump a PK1A constant pressure control kit would deliver 60 PSI to almost any size sprinkler zone you have and let you run hydrants with hoses as well.

 

[James Andrew]

For that much flow and using a 50/70 pressure switch you will need something like a J15S jet pump. Those bottom feeding "cistern" submersible pumps don't have the bearing structure and meat in them of a regular well pump submersible, and I haven't seen one last very long. With the J15S pump a PK1A constant pressure control kit would deliver 60 PSI to almost any size sprinkler zone you have and let you run hydrants with hoses as well.

1) I know the expected psi coming into a zone for Rainbird rotaries is expected to be 50 psi (even though they can function on less) , so am I correct in assuming the above pressure drops at furthest points, and the upsizing so to speak of the CSV from a 50 to a 60 psi makes sense?

2) That 1.5 hp Goulds pump I know is a quality brand, jet pump. I will be running this pump for 3-4 months each year. Would a 1.5 Flotec FP5172 Pump Sprinkler pump get the job done with a decent motor life? I know the issue is it does not sustain pressure well, yet it seems so odd they are designed for irrigation. 12 gpm 300 ft away cannot be all that hard for something called a sprinkler pump-- I must be missing something.

 

[James Andrew]

After looking at that price tag for 1.5 hp jet pumps, the submersible idea is looking real good. 1 hp, 4" hallmark for $145 . https://www.amazon.com/Hallmark-Ind...words=hallmark+1hp+220v&qid=1588386922&sr=8-1

So can a 90degree elbow be attached a few inches away from the discharge port? NB pump lying flat at bottom of tank in a sleeve.

 

[Reach4]

The upper float switch would control the filling of the tank by another pump. The lower switch inhibits the pump in the tank if the tank is out of water.

 

[Greenmonster123]

How many tanks will you have and what fills them?

 

[James Andrew]

I will have two tanks plumbed together with 2 inch pipe at bottom. So I was thinking of one float valve to fill from the well in one tank, and reach 4 ‘s design looks good minus the fill float in that tank, but ofcourse having the shutoff float for empty condition for irrigation pump.

 

[Greenmonster123]

I will have two tanks plumbed together with 2 inch pipe at bottom. So I was thinking of one float valve to fill from the well in one tank, and reach 4 ‘s design looks good minus the fill float in that tank, but ofcourse having the shutoff float for empty

Two totes is not a lot of water. You will only have about an hour and a half of watering at 12 gpm

 

[James Andrew]

Relative to cost of storage tanks, and space I wish allotted to this, and a watering schedule that will give time for refill , it would seem workable. I factored 1 hr 15 min of capacity, but not all zones will require the full 12 gpm, so hopefully more.

I am spending $40 on the tanks used. Figure 6-7 zones. In planting periods, I may have 4 hours of watering per day, in normal lawn watering it will go down to 2 hrs per day, given normal lawn watering will be staggered between zones to every other day or so. I had planned to water daily with two shifts (if needed) to permit two+ hours to refill the tanks break. So a 5 am watering, 9:30 am watering. That is roughly 3 hrs of watering by 11am. A late afternoon shift , would increase that to 4 1/2 hrs.

 

[James Andrew]

Still have the question on the PSI setting of CSV. Given pump and volume is not the limiting part of the equation- is the CSV setting throughout a long run (300ft, + 100 foot lateral for sprinkler zone) the same pressure the last sprinkler head will get? So, even if total friction loss to that sprinkler is -6 psi, as long as the pump can compensate for it, a 50 psi CSV means 50 psi at the sprinkler head...? So I really do not need a 60 psi CSV to be at 50 psi in the last head, correct?

 

[Valveman]

The constant pressure from the CSV will be at the pump. You will lose your 6 PSI after whichever CSV you install. 50 PS CSV means 43 PSI at the last head.